To better understand the UK data, I plotted the standardized difference by birth year, which I simply estimated as study publication date minus median subject ages. The studies presented by Lynn (2006) are in red; the studies that I have found are in blue. As for the latter, I had the guesstimate subject ages for a few samples. For the clinical and law aptitude tests, I assigned an age of 30, since in one of the data sets this was the median age of the applicants. For the industrial samples, I assigned an age of 40, since this is the median age of workers. I also correct the Situation Judgement Test difference up to 1, as in the US a difference of 0.5 on these tests corresponds to a cognitive differences of 1 (refer to Roth, et al. for the intercorrelations). As For the military samples, I assigned an age of 20, on the assumption that this was the median age of armed force applicants. I also had to estimate the standardized difference based on SAT scores, which I did by assuming a White standard deviation of 100. It should be noted that all of the studies were problematic in some way. They were either based on convenience samples (e.g., most of Lynn’s samples), based on unrepresentative samples (e.g., the clinical and law samples), unpublished (e.g., the gl-assessment sample), based on subtests scores and not full scale IQs (e.g., the MCS sample), and so on. Generally, the gaps shows a secular narrowing, but are not particularly consistent with the hypothesis that the cognitive ability gap has closed in the last generation.

I also plotted the standardized difference by test year. This, it can be seen, paints a somewhat different picture. This is due to my data points having a number of adult samples. Contemporaneous British Blacks age 30 and up, it seems, score around 0.8 standard deviations below Contemporaneous British Whites. An important unresolved question is whether or not the gap increases with age longitudinally as it does in the US. The narrowing shown when plotting data by birth date could represent a narrowing merely at young ages, for a given birth cohort, when the heritability of IQ is low, or it could represent a genuine narrowing of the population difference across age cohorts. The former would be consistent with a genetic hypothesis, while not the latter.

This then leaves a puzzle. The median birth year of the variousachievement samples, which show trivial to small gaps, is 1992. (The kids were 14-16, median 15, and the tests were taken between 2004 and 2010, median 2007.) Based on the trend line from the cognitive data below, the IQ gap should be 0.7 SD for this cohort. Given the correlation found between achievement scores and IQ (0.7), the minimum that the achievement gap should be, given this IQ difference, is .5 SD (0.7 x 0.7). Or conversely, given the achievement gap of maybe 0.2 SD — averaging the Black Caribbean and Black African scores — the most the cognitive gap should be is .3 SD (0.2/0.7). Why the disagreement in data? This, I suggest, is a question which warrants further investigation. Something is amiss in the UK.

There is a second puzzle here, too. The data shows that contemporaneous British Blacks age 30 and up are deficit in cognitive ability around 0.8 standardized units relative to Whites. The data implies that this magnitude of differences has been there for 40 years since testing began. If, for this last generation, the gap is greatly reduced, when did the narrowing begin? What is the magnitude of the gap for contemporaneous British Blacks age 20 and up?

Is there evidence of a general shift in the bell curve, or is it mostly pass levels on achievement tests? My impression from casual reading of newspapers is that there hasn’t been a huge surge of outstanding black talent into Oxford and Cambridge that you’d expect if the bell curve had actually shifted to the right. Perhaps, though, I’m wrong.

Upper class private school students are massively overrepresented at Oxbridge. There would be a lot more working class white people there if it reflected the true economic class composition of the right hand side of the bell curve. High IQ blacks are probably underrepresented there, just like high IQ poor whites.

A bleak portrait of racial and social exclusion at Oxford and Cambridge has been shown in official data which shows that more than 20 Oxbridge colleges made no offers to black candidates for undergraduate courses last year and one Oxford college has not admitted a single black student in five years.

The university’s admissions data confirms that only one black Briton of Caribbean descent was accepted for undergraduate study at Oxford last year.

Steve,
Refer to my post here. The graphs show the standardized test score gaps for math and reading. This would be equivalent to our NAEP gaps. In these graphs the actual test score differences are reported, not the pass rates or total point scores. So the lack of difference, on these fairly g-loaded tests, can no longer be dismissed as an artifact of a funky method of reporting (e.g., pass rates).

Ya, I’m not sure how to square these achievement results, which show little ethnic differences (but nonetheless large class differences), with the A level results, which seem to show a differences of at least a third of a standard deviation going into 2010. I presume that the latter accounts for the dearth of Caribbeanians at Oxford. Do you know anyone who might have a better handle on differences in the UK, who might able to explain the contradictions in the data? I think this is an issue deserving of more than a “Meh, whatever” response. I’m seeing only two plausible scenarios here: (1) there is, for this last generation, but a small (e.g., 0.3 SD) UK gap and no other factors are involved; by this account, the IQ data, suspect as it is, is dismissed, and no explanations is offered for the A-level gap. (2) there is a modest gap (e.g., 0.5 SD) but also systematic positive discrimination and motivational differences, reducing it to a trivial to small gap. Donno.

Apparently hereditarians are supposed to be quivering. A few reasons why i’m highly skeptical–i.e. pretty sure something’s wrong with the data here, not with the hereditarian model:

1) Crime.
It’s been well established that crime is anti-correlated with IQ. (Within population too.) Yet, all I’ve read suggest the UK, through its foolish immigration policies has imported a crime problem similar to the US. And that this crime is highly disproportionally committed by blacks. (There are routine black or white crime stories even though blacks are a tiny percentage of the UK population. Per capita it actually appears worse than the USA—don’t know if that’s true.) This heavy black crime just does not conform to your no\tiny IQ gap model. (And it’s the same population as the young adult test scores—there’s not a time delay issue here.)

2) Socio-Economic Gaps.
Your graphs indicate small\narrowing black\white IQ gaps, but then you have a chart showing the socio-economic gaps are robust. This would then imply that there is small\narrowing socio-economic gap between blacks and whites in the UK. I’ve heard absolutely no such claim. All the leftist rhetoric—“discrimination”, “exclusion”, etc.—seems in full play.

3) Successful Blacks.
Genetic equality and a small\narrowing measured (test score) gap should also quickly throw up successful blacks. Where are they? Yeah the BBC and the like have their mandatory black faces, but where are these brilliant young blacks? Where are the A-levels standouts? Where are the Oxbridge scholars?
The only account for this is either “discrimination!”—laughable (yeah, these folks are pushing away smart blacks, more the reverse)—or that the black standard deviation is much lower, so their mean is similar but not a lot of smart ones. Certainly the tighter SD is plausible\possible. There’s some evidence this is the case in the US.

4) The US
The US has a longer and much more robust data set and the results are quite clear. And they are clear even if you toss out the whole “black ghetto” issue and just look at middle class blacks, even middle class blacks in integrated suburbs in the same schools—Shaker Heights. The data are clear even if you compare within social classes and look at the scores of the kids of black college grads, or black professionals. We also have studies—and very clear everyday experience—that the more highly admixed blacks are smarter, the elite. Everything points to the same conclusion: A *large*–approximately one SD—racial IQ gap. (And it’s not “cultural bias” the gap on say the SAT is worse in math, the least biased and most culture-free area of human endeavor. Blacks are simply not as smart, *especially* at the higher level symbolic\analytical reasoning.)

A few thoughts on the possible causes for the discrepancy:
1) UK blacks may be smarter than in the US.
I think it’s incorrect to assert that there is no selection affect on immigration to the UK. Immigrants will tend to be somewhat smarter, more industrious to get themselves to the UK’s gravy train. This is true—though less so—of the refugee scam. You still have to be part of some group (clan, family) that was able to milk the refugee scam. Even the UK Somalis are probably on average smarter by some measurable amount than the Somali Somalis. US blacks are more representative. However, even they underwent strong selection, basically for health on the slave ships. But health correlates with IQ. But beyond that US blacks are mixed. Something around 20% on average. And the smarter blacks tend to have much higher admixture. How these two balance is unclear. But if UK Caribbean blacks have tended to test at IQs that are .8 SD lower than whites, I don’t find that anomalous.

2) Independent schools.
The UK has a strong independent (US: private) school tradition. The upper class, the successful, often sending their kids to independent schools, including the famous “public” schools. Wikipedia indicates it’s about 7% of the school age population. I would guess that is overwhelmingly white with a few Hindus and Chinese tossed in. I’m wondering if some of this data is gathered only from common (US: public) schools? That would then knock a bunch of elite white students out of the data.

3) “Special class”.
On the flip side, do these test data take into account “Special Class”. (I say the words and always think about the Bill Cosby routine :-) If there are a bunch of black students—proportionally *more* black students–not being counted because those students are in “special class”, then that compresses the difference. Likewise blacks drop out more. Any narrowing you see in the data as you move up in age must take this into account. (This is beyond the issue of the GSSC “pass” being a mediocre proxy.)

The possible exclusion of both or either “independent schools” or “special class” from the data are a classic “range restriction” problem, and distort the data. I would guess that probably both of them are involved here.

4) Score fiddling.
It’s not beyond the realm of possibility that the scores are simply being fiddled with. Two different levels come into play. First, racial egalitarians have declared war on these gaps. Most are quite content to have them exist, because they want the endless “progress war”. But some just plain want to expunge any racial differences as “thought crime”. Race does not exist, ergo the gaps can not exist … poof! Second, once these gaps are identified then “goodness” is “closing the racial achievement gap”. Districts, schools, teachers who can make this happen have achieved something and are to be rewarded. As a result, some find a way to *make* it happen. Since NCLB, the Atlanta schools had shown continual improvement … it’s heavily black student population marching upward in achievement. It was … a fraud. A huge fraud—not limited to one or two folks but a sizeable number of (black) administrators and teachers. I don’t know whether British schools in black areas are now in the hands of black administrators and teachers, but if they are I would consider rising black scores to be unremarkable.

5) Yob culture.
Also possible … whites are getting dumber. My rough take is that some *very* bad stuff has taken place in Britain. It seems to now have the worst white cultural environment. (Routine single parenthood. Yob culture.) I have a vague feeling that anglo-societies generally are more “cultural fragile” than say the Germanic ones. Anglo Saxons seem to have something close to the Germanic IQ, but we’re (I’m a mix myself) naturally a bit more prone to spear chucking—not going with the flow, flipping the guy off, doing our own thing. In short, more freedom oriented. Which has been good for creativity and progress … but which makes those societies more dependent on having a reasonable common civilizing culture. That civilizing culture seems to have broken down in the UK. It seems like a good 50% of the white population are just lost. And with the cultural breakdown—made worse having blacks around as negative role models—the white working class there is in rapid cultural decline.

So my thesis is that there are a lot more whites who are essentially acting “black”—not trying, flipping off school—than there were historically. This would tend to *widen* the SD in the test scores. And if the variance in test scores widens, then black\white gap in scores shrinks in SD units. This thesis would be somewhat hard to track because the tests are probably fiddled with year to year. But if there is a somewhat consistent set of raw test score data that shows a widening score variance, this would explain part of the gap shrinkage.